The invention concerns a hose connection for compressed air and fuel supply lines in motor vehicles as well as a nozzle for such a connection.
Such hose connections are disclosed, for instance, by FR 2652872 wherein they are formed by forcing a hose onto a penetrating nozzle. In order to obtain an axial securement of the hose on the nozzle, FR 2652872 proposes generally radially protruding, projecting rings on the circumferential surface of the nozzle. Upon the pushing of a hose, which is composed of an elastic plastic, onto the nozzle, the hose is radially expanded and thus passes over the radial projections. By the elastic tendency toward a return to an original shape, the inner wall of the hose is pressed against the circumferential surface of the nozzle and correspondingly against the projecting rings, whereby an axial and non-rotating securement of the hose is obtained and a sealing at the separating zone between the hose and the nozzle takes place.
A cursory view of this as being a very simple connection technology hides, however, substantial problems in real practice. In order to assure a satisfactory sealing and tight connection, a relatively high surface pressure is necessary, which necessitates a relatively large radial expansion of the hose. This stress brings about the danger of internal crazing and tension fissures in the hose, particularly in the areas of the projecting rings. Such material failures reduce the integrity of the tight seal and lessen security of the connection between hose and nozzle.
Added to this difficulty are mechanical, thermal and chemical effects throughout what is often a long operating life of a motor vehicle. Material fatigue is evidenced by hose relaxation, which is especially noticeable in extremely radially-stretched hoses. In the case of conventional hose connections, radial expansions up to double the original inside diameters are quite common.
Thus, an objective of the invention is to propose a hose connection, which during the lifetime of a motor vehicle assures both mechanical connection integrity as well as tight sealing.
This objective is achieved by a hose connection of the type stated by means of the features of the invention. Accordingly, a hose composed of:
or a mixture of PA6 and PE is suggested. The outside diameter of the hose or that of the projecting rings, discussed below, is 40 to 60% larger than its inside diameter. Experience has shown that within this range of widening, in the case of hoses made of the above named materials, a reliable mechanical connection and sealing of the said hose is assured over the entire lifetime of the motor vehicle. By the planned co-action between the nozzle and the hose, no fissure formation nor crazing appears upon the pushing on of the hose. Particularly good results are achieved when the outside diameter of the projecting rings, for instance, were less than or equal to 1.8 times the hose diameter. As a rule, hoses are produced by an extrusion process. As a result of this, there occurs an orientation of the macromolecules of the polymerized materials along the longitudinal extent of the hose. The greater the degree of this orientation, the less the danger of crazing and tension fissuring. Advantageously, a material which exhibits a shrinkage of 2 to 6% when measured in an axial direction is provided. The shrinkage, which is a measure of the degree of orientation of the macromolecules, is determined in a test in which, for instance, a HDPE-hose is heated for 1 hour at a temperature less than its softening point upon heating, the molecules stretched by the extrusion process return to their original random and thus shortened condition. Decreased hose length is measured during this time.
In accordance with the invention, the pushing of the hose end onto the nozzle is made easier. Beyond that, the expansion of the hose end is accomplished, not suddenly, but gradually in a material protective manner. Advantageously, two projecting rings are available, the diameters of which respectively increase in the direction (see arrow 5) of hose thrust in accord with the invention. A particularly advantageous embodiment of the invention provides that the first projecting ring is divided into three longitudinal sections of differing slopes. By means of this formation, and particularly because of the central cylindrical section, the action toward position sealing is increased. In consideration of an improved sealing action and a protective penetrative insertion of the nozzle into the hose, advantageous angles of inclination are suggested by the invention.
In the case of an embodiment in accord with the invention, by means of the sharply edged design of the first projecting ring with its lesser diameter, an axial fix of a hose by means of a still allowable notch-effect is achieved. The second projecting ring with its greater diameter has, on the other hand, a rounded off edge, whereby a lessened notch-effect is available but with a still sufficing axial fix. Alternatively, the invention provides for a reduction in the extension of a hose at its end section. In the case of this end section of a hose, the danger of fissures and crazing as a result of an extended time of operation is particularly great.
By the demands of torsion at the hose connection, the danger is present that the holding friction between the nozzle and the hose material is overcome, whereby the hose end rotates in respect to the nozzle. When this occurs, faulty sealing can result. By flattened zones on the circumferential surfaces of the nozzle in accord with the invention, a rotation-prevention means is created. The outer hose wall lies in a shape-sealing closure with this flattened zone. Advantageously, the flattened zones are located between that end of the nozzle remote from the hose and the second projecting ring. An additional hindrance to hose rotation on the nozzle is assured by shaping as provided in another possible aspect of the invention.